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    How climate models and attribution science work

    Climate models are mathematical representations of the atmosphere, ocean, land and sea ice, solved on a 3D grid, and they let scientists test what the climate would look like with and without human influence.[1][2] That comparison underpins the IPCC finding that human influence has unequivocally warmed the planet, and rapid "event attribution" studies now apply it to individual heatwaves, floods and droughts.[3][4]

    Editor reviewedUpdated Climate science and carbon removalEnergy and climateScience

    What a climate model is

    A climate model is a giant computer program that follows the laws of physics. It splits the planet into a 3D grid of boxes and calculates how air, water, ice and land exchange heat and moisture in each box.[1] Because scientists cannot run experiments on the real Earth, they run them in models instead, for example by switching human greenhouse gas emissions on or off.[2]

    NOAA’s Geophysical Fluid Dynamics Laboratory describes a climate model as a mathematical representation of the atmosphere, land surface, ocean and sea ice and their interactions, with equations solved at each point of a three-dimensional grid.[1] Models are used for controlled experiments, for detection and attribution of observed change, and for projections from seasons to centuries.[2] Modelling centres coordinate experiments through the Coupled Model Intercomparison Project; the IPCC’s 2021 assessment relied on its sixth phase, CMIP6, and found observed warming within the ensemble’s very likely range.[5]

    Climate sensitivity: the key number

    Equilibrium climate sensitivity is the long-term warming from doubling atmospheric CO2. The IPCC’s best estimate is 3 °C, with a very likely range of 2–5 °C.[6] The IPCC also found a near-linear link between cumulative CO2 emissions and warming, about 0.45 °C per 1,000 billion tonnes of CO2, which is the basis of carbon budgets.[7]

    Detection and attribution of global warming

    Detection asks whether a change is outside natural variability; attribution asks what caused it. Comparing observations with model runs that include and exclude human influence led the IPCC to state that it is unequivocal that human influence has warmed the atmosphere, ocean and land.[3][2] The annual Indicators of Global Climate Change study puts human-induced warming at 1.37 °C in 2025 against 1.39 °C observed, and concludes that nearly all warming over the last decade is human-driven.[8][9][10]

    Attributing extreme events

    Event attribution asks a narrower question: did climate change make this particular heatwave or flood more likely, or worse? Scientists compare how often such an event happens in today’s climate with how often it would happen in a cooler, pre-industrial climate.[4]

    World Weather Attribution, set up in 2014 with partners including Imperial College London and the Dutch weather service KNMI, combines observations and models to estimate changes in an event’s likelihood and intensity relative to pre-industrial conditions.[11][4] It publishes rapid studies, and 26 of them have also been published in peer-reviewed journals.[12] The IPCC assessed that some recent hot extremes would have been extremely unlikely to occur without human influence.[13]

    A 2025 analysis by World Weather Attribution and Climate Central found that the 0.3 °C of warming since 2015 adds on average 11 hot days a year worldwide, and that this would rise to 57 extra hot days at 2.6 °C of warming.[14]

    Where the field is heading

    The IPCC’s seventh assessment cycle (AR7) is under way, but governments had not agreed its timeline as of the 64th session in March 2026.[15] The 65th session meets in Addis Ababa on 12–16 October 2026.[16] See ipcc for how the assessment process works.

    Questions readers ask

    How do scientists know warming is caused by humans?

    The IPCC assessed that it is unequivocal that human influence has warmed the atmosphere, ocean and land, and the 2025 indicators study found nearly all warming over the last decade is human-driven.[3][10]

    Can a single heatwave be blamed on climate change?

    Attribution studies estimate how much more likely or intense an event became. The IPCC found some recent hot extremes would have been extremely unlikely without human influence.[4][13]

    How sensitive is the climate to CO2?

    The IPCC's best estimate is that doubling CO2 leads to 3 °C of long-term warming, with a very likely range of 2–5 °C.[6]

    Are climate models accurate?

    For global temperature, observed warming lies within the very likely range of the CMIP6 models used in the IPCC's 2021 assessment.[5]

    Sources

    Each numbered claim is a statement we checked against the sources listed with it. Status shows how well established it is.

    1. [1]

      NOAA describes a climate model as a mathematical representation of the atmosphere, land surface, ocean and sea ice and their interactions, solved on a three-dimensional grid of cells covering the Earth. confirmedas of 2026-10-10

      • Climate Modeling · NOAA Geophysical Fluid Dynamics Laboratory (retrieved 2026-10-10)
    2. [2]

      NOAA lists the uses of climate models as controlled experiments on parts of the climate system, detection and attribution of climate changes, and projections from seasons to centuries ahead. confirmedas of 2026-10-10

      • Climate Modeling · NOAA Geophysical Fluid Dynamics Laboratory · Uses of climate models (retrieved 2026-10-10)
    3. [3]

      The IPCC's Sixth Assessment Report states that it is unequivocal that human influence has warmed the atmosphere, ocean and land. confirmedas of 2021-08-09

    4. [4]

      World Weather Attribution uses observations and computer models to quantify how climate change has altered the intensity and likelihood of an extreme weather event, comparing today's climate with pre-industrial conditions. confirmedas of 2026-10-10

    5. [5]

      The IPCC's 2021 assessment used simulations from the Coupled Model Intercomparison Project Phase 6 (CMIP6) of the World Climate Research Programme, and observed warming lies within the very likely range of the CMIP6 ensemble. confirmedas of 2021-08-09

    6. [6]

      The IPCC's best estimate of equilibrium climate sensitivity, the long-term warming from a doubling of CO2, is 3 °C, with a very likely range of 2–5 °C. confirmedas of 2021-08-09

    7. [7]

      The IPCC found a near-linear relationship between cumulative CO2 emissions and warming, with each 1,000 billion tonnes of CO2 likely causing 0.27–0.63 °C of warming (best estimate 0.45 °C). confirmedas of 2021-08-09

    8. [8]

      The Indicators of Global Climate Change 2025 study estimated human-induced warming at 1.37 °C above 1850–1900 in 2025, rising at about 0.27 °C per decade over 2016–2025. confirmedas of 2026-06-11

    9. [9]

      The same study put observed global surface warming in 2025 at 1.39 ± 0.13 °C above 1850–1900. confirmedas of 2026-06-11

    10. [10]

      The indicators team concluded that nearly all of the warming over the last decade is driven by human activities. confirmedas of 2026-06-11

    11. [11]

      World Weather Attribution was set up in 2014 and works with Imperial College London, the Royal Netherlands Meteorological Institute (KNMI) and the Red Cross Red Crescent Climate Centre. confirmedas of 2026-10-10

    12. [12]

      World Weather Attribution says 26 of its rapid studies have also been published in peer-reviewed journals. confirmedas of 2026-10-10

    13. [13]

      The IPCC found that some recent hot extremes would have been extremely unlikely to occur without human influence on the climate. confirmedas of 2021-08-09

    14. [14]

      A 2025 World Weather Attribution and Climate Central analysis found the world now has on average 11 more hot days per year from the 0.3 °C of warming since 2015, rising to 57 extra hot days a year at 2.6 °C of warming. confirmedas of 2025-10-16

    15. [15]

      At its 64th session in Bangkok, which closed on 27 March 2026, the IPCC made no formal decision on the timeline of its Seventh Assessment Report, though governments said they want it agreed at the next session. confirmedas of 2026-03-27

    16. [16]

      The IPCC's 65th plenary session is scheduled for 12–16 October 2026 in Addis Ababa, Ethiopia. confirmedas of 2026-10-08

    Revision history (1)
    1. Page created.

    Created Oct 10, 2026. Last reviewed by an editor on Oct 10, 2026. Next scheduled review: Jan 10, 2027.

    Cite this page

    "How climate models and attribution science work." ContentLora, updated Oct 10, 2026. https://contentlora.com/explain/how-climate-attribution-works

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